1. Field of the Invention
The invention relates to the field of electronics. More specifically, the invention relates to electric connections used in power modules.
2. Background of the Invention
An inverter is commonly used to convert direct current (xe2x80x9cDCxe2x80x9d) to alternating current (xe2x80x9cACxe2x80x9d) to power a three-phase load, such as a three-phase motor, or, alternatively, to convert AC from a three-phase source to DC. The inverter commonly contains six switches. Power modules often contain one or more pairs of complementary switches. The power module typically includes silicon dice on substrates that are secured to the module baseplate. Each switching pair has a positive or xe2x80x9chighxe2x80x9d side switch and a negative or xe2x80x9clowxe2x80x9d side switch for controlling the flow of electric current. Each switching pair is referred to herein as a xe2x80x9chalf bridge.xe2x80x9d The xe2x80x9chigh sidexe2x80x9d of the bridge contains the positive switches, and the xe2x80x9clow sidexe2x80x9d contains the negative switches. By the term xe2x80x9cswitchxe2x80x9d is meant a switching device such as an insulated gate bipolar transistor (xe2x80x9cIGBTxe2x80x9d) or Bipolar Junction Transistor (xe2x80x9cBJTxe2x80x9d) or Metal Oxide Semiconductor Field Effect Transistor (xe2x80x9cMOSFETxe2x80x9d), either singly or in parallel.
Elements may be described herein as xe2x80x9cpositivexe2x80x9d or xe2x80x9cnegative.xe2x80x9d An element described as xe2x80x9cpositivexe2x80x9d is shaped and positioned to be at a higher relative voltage than elements described as xe2x80x9cnegativexe2x80x9d when the power module is connected to a power source. xe2x80x9cPositivexe2x80x9d elements are positioned to have an electrical connection that is connectable to the positive terminal of a power source, while xe2x80x9cnegativexe2x80x9d elements are positioned to have an electrical connection that is connectable to a negative terminal, or ground, of the power source. Generally, xe2x80x9cpositivexe2x80x9d elements are located or connected to the high side of the power module and xe2x80x9cnegativexe2x80x9d elements are located or connected to the low side of the power module.
In a typical power module configuration, the high side switches are on one side of the module opposite the corresponding low side switches. A positive DC lead from a power source such as a battery is connected to a conducting layer in the high side of the substrate. Likewise, a negative DC lead from the power source is connected to a conducting layer in the low side of the substrate. The high side switches control the flow of current from the conducting layers of each high side substrate to output leads. Output leads, called xe2x80x9cphase terminalsxe2x80x9d transfer alternating current from the three pairs of switches, or half bridges, to the motor.
Power modules typically have three half bridges combined into a single three-phase switching module, or single half-bridge modules that may be linked together to form a three-phase inverter. As would be understood by one of ordinary skill in the art, the same DC to AC conversion may be accomplished using any number of half bridges, which correspond to a phase, and each switching pair may contain any number of switching devices. For simplicity and clarity, all examples herein use a common three phase/three switching pair configuration. However, the invention disclosed herein may be applied to a power module having any number of switches.
Current flows from the power source through the positive DC lead to the conducting layer on the high side substrate. Current is then permitted to flow through one or more switching device on the high side to a conducting layer, commonly referred to as a phase output layer, on the low side. A phase terminal lead allows current to flow from this conducting layer on the low side to the motor. The current then flows from the motor to the corresponding conducting layer on the low side of a second switching pair through the low side switches and diodes to the negative DC lead to the power source.
Current flowing through various inductive paths within the module transiently stores energy which increases energy loss, reduces efficiency, generates heat. When the flow of current changes, as in such a high frequency switching environment, large voltage overshoots often result, further decreasing efficiency. In addition, the DC terminals are commonly attached to one end of the power module, which forces current to travel further to some switches for some switching configurations, than for others, resulting in non-uniform current loops. Current loops that are not uniform result in uneven or inefficient motor performance. Additional materials regarding efficient configurations of power modules may be found in application Ser. No. 09/957,568 filed herewith), entitled xe2x80x9cSubstrate-Level DC Bus Design to Reduce Module Inductance,xe2x80x9d application Ser. No. 09/957,001, filed herewith), entitled xe2x80x9cEMI Reduction in Power Modules Through the Use of Integrated Capacitors on the Substrate Level,xe2x80x9d and application Ser. No. 09/882,708 entitled xe2x80x9cLeadframe-based Module DC Bus Design to Reduce Module Inductancexe2x80x9d which are hereby incorporated by reference in their entirety.
Present inverter power module designs typically require wire bonding or direct soldering of power terminals or jumpers to obtain acceptably high current carrying capacity with minimal contact resistance. However, soldering large terminals and wire bonding are energy intensive and time consuming manufacturing operations.
These and other problems are avoided and numerous advantages are provided by the device described herein.
The present invention provides an electrical connector for use in a power module that utilizes a press contact to avoid the use of wire bonding or direct soldered contacts. Such electrical connectors are useful in power modules where power module components, such as the DC bus, are incorporated into the power module to reduce voltage overshoots and increase switching efficiency. Connections are made between various components in the power module by pressing a connector between two components.
Elements may be described herein as xe2x80x9cadjacentxe2x80x9d to another element. By the term xe2x80x9cadjacentxe2x80x9d is meant that in a relationship so characterized, the components are located proximate to one another, but not necessarily in contact with each other. Normally there will be an absence of other components positioned in between adjacent components, but this is not a requirement. By the term xe2x80x9csubstantiallyxe2x80x9d is meant that the orientation is as described, with allowances for variations that do not affect the cooperation and relationship of the so described component or components.
In one aspect the present invention, an electrical connector for use in a power module includes a first end portion for forming an electrical connection with as substrate, a second end portion, and a compliant portion situated between the first and second end. The compliant portion includes a compressed position and a decompressed position. The first end portion is configured for forming an electrical connection with a substrate if the compliant portion is in the compressed position.
In another aspect, the first end portion extends outward from the second end portion. In yet another aspect, the first end portion extends inward from the second end portion. In still another aspect, the compliant portion is curved.
In one aspect of the invention, the electrical connector includes a system for compressing the compliant portion from the uncompressed position to a compressed position. In one embodiment, the system includes downward pressure applied to the compliant portion. In another embodiment, the system includes a component placed on the second end portion for exerting downward pressure to the compliant portion. In yet another embodiment, the system includes a fastener.
In yet another aspect, the present invention is directed to a DC bus for use in a power module. The DC bus includes a positive DC conductor bus plate and a negative DC conductor bus plate. A connector is fastenable from at lease one of the positive or negative DC conductor bus plates. The connector includes a first end portion for forming an electrical connection with as substrate, a second end portion, and a compliant portion situated between the first and second end. The compliant portion includes a compressed position and a decompressed position. The first end portion is configured for forming an electrical connection with a substrate if the compliant portion is in the compressed position.
The connector and DC Bus disclosed herein provide a connection between electrical components in a power module that does not require wire bonding or soldering. The invention provides for relatively easy assembly and reduced cost of manufacture. The invention may be utilized in any power module configuration. However, the present invention is particularly useful in power modules where power module components, such as the DC bus, are incorporated into the power module to reduce voltage overshoots and increase switching efficiency.
These and other advantages will become apparent to those of ordinary skill in the art with reference to the detailed description and drawings.